Organic photoconductive element with interlayer and adhesion promoting additive

ABSTRACT

The present invention relates to photosensitive members for electrophotography and more particularly to photosensitive layers prepared from organic photoconductive materials. The present invention provides photosensitive members which have been improved with respect to resistance to electric breakdown, adhesive ability, flexibility, and the like thereof and which are of great practical value. In accordance with the present invention, between a substrate and an organic photoconductive layer is interposed a barrier layer which is comprised mainly of copolymers comprising alkyl vinyl ethers and maleic anhydride or of composites of alkyl vinyl ethers/alkyl half esters of maleic acid copolymers and polyvinyl pyrrolidone or copolymers thereof. The photoconductive layer per se has been improved by incorporating vinylidene chloride/acrylic ester copolymers into the organic photoconductive layer.

United States Patent 1 91 Matsuno et al.

[ June 3, 1975 [75] Inventors: Hiroshi Matsuno; Ichiro Endo, both of Tokyo, Japan [73] Assignee: Canon Kabushiki Kaisha, Tokyo,

Japan [22] Filed: Nov. 5, 1973 [21] Appl. No.: 412,828

[30] Foreign Application Priority Data Nov. 6, 1972 Japan 47-110942 [52] US. Cl. 96/].5; 96/16; 117/218', 1l7/72; 117/161 UA; 117/161 UP, 117/161 UC [51] Int. Cl. G03q 5/06 [58] Field of Search 96/l.5, 1.6

[56] References Cited UNITED STATES PATENTS 3,421,891 l/l969 lrami et al. 96/16 3,488,189 6/1970 Mayer et a1 3,615,403 10/1971 Cheng 1. 3,669,657 6/1972 Adams et a1 3,682,629 8/1972 Shimizu et al. 3,704,121 1l/1972 Makino et a1 96/l.5 3,712,812 l/l973 Van Paesscheu et al. 96/l.5

3,745,005 7/1973 Yoerger et a1 96/1.5

FOREIGN PATENTS OR APPLICATIONS 562,337 5/1958 Belgium 96/1.5

Primary Examiner-Roland E. Martin, Jr. Attorney, Agent, or FirmFitzpatrick, Cella, Harper & Scinto [57] ABSTRACT The present invention relates to photosensitive members for electrophotography and more particularly to photosensitive layers prepared from organic photoconductive materials. The present invention provides photosensitive members which have been improved with respect to resistance to electric breakdown, adhesive ability, flexibility, and the like thereof and which are of great practical value.

In accordance with the present invention, between a substrate and an organic photoconductive layer is interposed a barrier layer which is comprised mainly of copolymers comprising alkyl vinyl ethers and maleic anhydride or of composites of alkyl vinyl ethers/alkyl half esters of maleic acid copolymers and polyvinyl pyrrolidone or copolymers thereof. The photoconductive layer per se has been improved by incorporating vinylidene chloride/acrylic ester copolymers into the organic photoconductive layer.

15 Claims, N0 Drawings ORGANIC PHOTOCONDUCTIVE ELEMENT WITH INTERLAYER AND ADHESION PROMOTING ADDITIVE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to photosensitive members for use in forming electrophotographic images, in which organic photoconductive layers are used.

2. Description of the Prior Art The hitherto used organic photoconductive materials include high or low molecular weight organic compounds such as poly-N-viny lcarbazole, brominated poly-N-vinylcarbazole, polyvinyl anthracene, oxadiazoles, acylhydrazones, and the like. They have been used, if desired, in admixture with sensitizing agents to prepare photosensitive materials for use in electrophotography.

The organic photoconductive materials are excellent in respect of transparency, film forming ability, capability to select charging polarity, smoothness of formed surface, and the like, and the high molecular weight compounds are capable of forming a film.

However, the photosensitive member which is prepared by providing the organic photoconductive compound alone on the conductive substrate is susceptible to electric breakdown, and it is not of practical value in electrophotography. In addition, the photoconductive materials lack flexibility and cannot be commercially employed.

The photosensitive members using the conventional photoconductive compounds are often subject to electric breakdown in corona discharging and thus white spots are formed in developed images, which results in remarkable deterioration of printed images.

Some dificulties have been encountered in avoiding such drawbacks. For instance, a resinous adhesive layer has been provided between the organic photoconductive layer and the substrate. However, there has not been found any suitable resins capable of forming a practically effective film, which resists electric breakdown, without materially decreasing sensitivity of the photoconductive layer.

Moreover, such photosensitive members have not been usable in electrophotography wherein the photosensitive member is used repeatedly, for the reasons that it is subject to deteriorations such as decreasing in amount of charge, residual of photomemory due to lowered initial charging rate, decreasing in sensitivity, and the like as well as electric breakdown. Almost no research has been made on the application of the photosensitive member comprising organic photoconductive materials to electrophotographic processes wherein the photosensitive member is subjected to repeated charging, exposing to light, developing, transferring, and the like, and furthermore, the aforementioned drawbacks have not been recognized.

The construction of the photosensitive member comprising a substrate, a photoconductive layer, and a barrier layer interposed between them is known in the art. However, materials which are commercially and effectively usable in preparing a barrier layer have not been found and, needless to say, such materials have not been used in electrophotographic processes in which the photosensitive member is repeatedly used. Therefore effects of the barrier layer on photosensitive members which are repeatedly used have not been found at all.

The organic photoconductive member per se is not satisfactory in the points of strength and plasticity and in practical usage, there occur great drawbacks of peeling of layer, cracking of photosensitive member, and the like.

Many attempts have been made to avoid the above drawbacks by adding plasticizers, resins, and the like but, however satisfactory results have not been obtained.

That is, the conventional plasticizer, resin, or the like such as chlorinated polyphenyl in the amount equal or close to that of the above high molecular weight photo conductive compound is required for improving the flexibility of the photoconductive layer, which results in deterioration of sensitivity, injury to the human body, and the like. Generally, low molecular weight plasticizers are also required to be added in a large amount as in the chlorinated polyphenyl so as to obtain sufficient effect thereof, which also results in deterioration of sensitivity.

On the contrary, sufficient effect can be attained by using a small amount of high molecular weight compounds. For instance, it is known that the addition of polycarbonate of about 20% brings about good results. However, the conventional high molecular weight photoconductive compounds are generally of high crystallinity and have molecular weights of more than one million and therefore, they are not miscible with other polymers. As a result, the use of high molecular weight compounds as the plasticizer is not effective.

SUMMARY OF THE INVENTION The primary object of the present invention is to overcome the aforementioned drawbacks and to provide excellent organic photoconductive materials for electrophotosensitive members.

The secondary object of the present invention is to prevent electric breakdown and deterioration of a photosensitive member being repeatedly used in electrophotography by providing a specific barrier layer.

Another object of the present invention is to provide organic photoconductive members of high miscibility, flexibility, and adhesive ability.

Other objects and advantages of the present invention will be apparent from the following explanation.

PREFERRED EMBODIMENT OF THE INVENTION The present invention relates to photosensitive members for electrophotography characterized in that between an organic photoconductive layer and a substrate is provided a barrier layer which comprises alkyl vinyl ether maleic anhydride copolymers or composites of alkyl vinyl ethers alkyl half esters of maleic acid copolymers and polyvinylpyrrolidone or copolymers thereof.

The volume resistivity of the barrier layer as used herein should be adjusted to a proper value 10 to lO fl-cm) so that electric breakdown may be completely prevented and deterioration of the photosensitive member being repeatedly used may be prevented without adversely affecting photosensitivity, image properties, and the like thereof. It has been found that proper materials for the barrier layer which completely satisfy the above requirements include alkyl vinyl ether /maleic anhydride copolymers, and composites of alkyl vinyl ethers alkyl half esters of maleic acid copolymers and polyvinyl pyrrolidone or copolymers thereof (complex).

Alkyl vinyl ethers herein include methyl vinyl ether, ethyl vinyl ether, isopropyl ether, hexyl vinyl ether, dodecyl vinyl ether, and the like. Higher molecular weight alkyl vinyl ethers generally tend to lose copolymerizability thereof with maleic anhydride or alkyl half esters of maleic acid and to result in lower film forming ability of the formed copolymers. Thus the carbon number of the alkyl group is preferred to be not more than 12, and particularly not more than 6 is preferred. Alkyl half esters of maleic acid herein include methyl half ester of maleic acid, ethyl half ester of maleic acid, iso-propyl half ester of maleic acid, n-butyl half ester of maleic acid, iso-butyl half ester of maleic acid, n-hexyl half ester of maleic acid, benzyl half ester of maleic acid, octyl half ester of maleic acid, and the like.

As polyvinyl pyrrolidone herein, those having an average molecular weight of 4,000 to 360,000 may be used, and those having an average molecular weight of 40,000 to 360,000 are most preferred in view of film forming ability as the composite thereof.

As vinyl monomers to be copolymerized with vinyl pyrrolidone, there may be used styrene, vinyl chloride, vinyl acetate, methacrylate, acrylate, acrylamide, acrylonitrile, vinyl ether, vinyl imidazole, ethylene, and the like. The molar ratio of the vinyl monomer to vinyl pyrrolidone is preferred to be in the range of 7 3 to 3 7.

The photosensitive member of the present invention prepared by providing a barrier layer composed mainly of the aforementioned composite between an organic photoconductive layer and a substrate is prevented from electric breakdown and deterioration in repeated developing. Furthermore, in accordance with the present invention, film properties of a photosensitive layer, such as adhesive ability, flexibility, tensile strength, and the like are markedly improved and, thus excellent photosensitive members for electrophotography having stable properties are obtained.

As the substrate as herein used, there may be employed any conventional one usable in electrophotographic photosensitive members, such as aluminum, copper and like plates; papers and aluminum laminated papers; surface active agent-incorporated synthetic resin film and tertiary ammonium salts-treated conductive synthetic resin film; glass, paper, and synthetic resins deposited with metals, metal oxides, and metal halides on the surface thereof; and the like.

Other representative substrates are as follows: substrates which were prepared by depositing a thin film of titanium oxide, stannic oxide, copper iodide, or the like as a light permeable photoconductive layer on transparent base films such as polyethylene glycol terephthalate (trade names: Mylar, Tetron, Lumirror, Daiafoil), cellophane, cellulose acetate, polycarbonate, nitro cellulose, polyvinyl chloride, and the like; and substrates which are prepared by providing a thin coating of antistatic agents composed mainly of surface active agents known as low resistant materials on the aforementioned base films. In some cases, the above base films per se are used as the substrate. Generally, there may be used those having volume resistivity of below lO Q-cm, preferably below 10 Q cm.

The barrier layer of the present invention is formed on the aforementioned substrates according to a process which comprises dissolving the composites of the present invention in a proper solvent, adjusting the viscosity of the solution so obtained to those suitable for coating, coating the solution in the conventional coating manners, and thereafter air-drying or drying by heating. At this stage, plasticizers which are wellmiscible with the aforementioned composites, such as methyl vinyl ether, trichloro ethyl phosphate, tricresyl phosphate, diphenyl chloride, and the like can be added to the composites in the amount of 10 to 50% to further facilitate film properties. The barrier layer so obtained is sufficiently flexible and strong.

Pigments may be, if necessary, added in the required amount at the step of preparing the coating solution.

The thickness of the barrier layer of the present invention is preferably below 10 and more particularly, good results can be obtained in the range of 2 to 7p thickness. In the photosensitive master to be repeatedly used, a barrier layer of about l,u. thickness can be used with excellent results. It has been, however, confirmed experimentally that the thickness of over 10a adversely affects the photosensitivity of the photosensitive member.

Thus, when the thickness of the barrier layer is made below 10a, decreasing in sensitivity can be prevented and moreover, when the barrier layer of the present invention is provided, electric breakdown and deterioration encountered in repeated uses can be completely prevented.

The photosensitive member of the present invention can be produced by superposing a photoconductive layer on the barrier layer.

All the organic photoconductive materials as known in the art may be used in the present invention and particularly polymerizable photoconductive materials are effectively employed. Such polymerizable photoconductive materials include chlorinated polyvinyl carbazoles such as poly 9 vinyl carbazole, poly 3 chloro 9 vinyl carbazole, poly 3,6- dichloro 9 vinyl carbazole, and the like; brominated polyvinyl carbazoles such as poly-3-bromo-9-vinyl carbazole, poly-3,6- dibromo-9-vinyl carbazole, and the like; poly-3-methyl- 9-vinyl carbazole; copolymers from monomers selected from the group of 9-vinyl carbazole, 3,6-dichloro-9- vinyl carbazole, 3-bromo-9-vinyl carbazole, 3,6- dibromo-9-vinyl carbazole, 3-methyl-9-vinyl carbazole, and the like; poly-9-vinyl carbazole derivatives such as chlorinated poly-9-vinyl carbazole, brominated poly-9- vinyl carbazole, iodinated poly-9vinyl carbazole, cyanated poly-9-vinyl carbazole, thiocyanated poly-9-vinyl carbazole, and the like. Furthermore, there may be used organic photoconductive materials containing aromatic or hetero rings as shown below:

The photoconductive materials as herein used are not limited to those as noted above, and a wide variety of organic photoconductive materials such as anthracene, pyrene, perylene, triphenyl pyrazoline derivatives, acyl hydrazone derivatives, and the like may be also used. In particular, 9-vinyl carbazole, derivatives thereof, and polymers thereof are effectively used in the present invention.

The sensitizing compounds are effectively added to the photoconductive materials as listedabove. The sensitizing compoundsinclude chemically sensitizing compounds, dye sensitizing compounds, and the like. As the chemically sensitizing compound, compounds which are generally known to be electron attractive may be given as follows: tetracyano ethylene, tetracyano quino dimethane, bromanil, chloranil, benzoquinone, naphthoquinone, anthracene, anthraquinone derivatives, P-nitro phenol, picric acid, 1,3,5-trinitro benzene, monochloro acetate, and the like.

The dye sensitizing compounds include Crystal Vio let Rhodamine B, Rhodamine 6G, Methylene Blue, Rose Bengal, Methyl Violet, cyanine dyes having nitro group, triarylmethane dyes having carbazole ring, and

' the like.

As the plasticizer, hydrochloric acid diphenyl diocthyl phthalate, tricrezyl phosphoric acid, cumarone resin, chlorinated paraffin, and the like may be used.

It is known that the aforementioned photoconductive materials are useful for electrophotography. It is considered that the high photoconductivity of the materials is based upon overlapped 1r bond due to the specific crystalline structure thereof.

However, such crystallinity readily causes cracks in the formed film and deteriorates adhesive ability thereof to a substrate, which are considered to be serious drawbacks in practical usage.

It has been found that the compound of the following formula is greatly effective for the high molecular weight photoconductive member.

In addition it has been found that the aforementioned high molecular weight photoconductive member in which the vinylidene chloride-acrylic ester copolymer is added in an amount of 1% to by weight based upon the photoconductive member exhibits excellent adhesive ability to the substrate and excellent flexibil- 1ty.

The addition of the copolymer in an amount beyond the upper limit deteriorates the miscibility of the high molecular weight photoconductive member with vinylidene chloride-acrylic acidester copolymer and further deteriorates the transparency of the formed film. When the copolymer is below the lower limit. the advantages of the present invention are difficult to obtain.

The addition amount of the copolymer of the invention is small as compared with those of the conventional plasticizers and thus the present invention is considered to have the advantages that sufficiently good results can be obtained in such small addition amount. Therefore, decreases in sensitivity of the photosensitive plate are minimized. The aforementioned vinylidene chloride-acrylic ester copolymers may be used solely or preferably in admixture with other plasticizers. Such plasticizers include cumarone resin, chlorinated paraffin, sulfonamide resin, epoxy resin, poly-isocyanates, styrene oligomers, and the like.

The invention will be understood more readily with reference to the following examples; however, these examples are intended to illustrate the invention and are not to be construed to limit the scope of the invention.

EXAMPLE 1 A treating agent of low resistivity, an aqueous poly- (N,N-dimethyl-3,5-methylene) piperidinium solution was coated on a thick poly-ethyleneterephthalate film and dried to prepare a light-transmittable conductive layer.

Thereafter, a 10% by weight solution of methyl vinyl ether maleic anhydride copolymer (GANTREZ, AN- l39, supplied by GAP) and polyvinylpyrrolidone (PVP-K90, supplied by GAF) (in the weight ratio of 5 5) in a mixture of ethyl alcohol and N,N'-dimethyl formamide (5 5) was coated on the photoconductive layer as formed above in a film thickness of 3 to 4p. and dried to prepare a barrier layer. The thusobtained film was greatly transparent, strong, and flexible and had an excellent capability to adhere to the photoconductive layer. On the barrier layer was coated (8g./m and dried a photosensitive agent of comprising a solution of benzene and chlorobenzene (l 1) containing polyvinylcarbazole and crystal violet to prepare a photosensitive layer. The light transmittable organic photocon ductive film so obtained was subjected to charging and exposing to light in a conventional manner to obtain reduced images, which were further developed by a wetdeveloper. As a result, extremely excellent positive images were obtained.

On enlarging and projecting the positive image with a projector, it was found that with the conventional photosensitive film in which the photosensitve layer was provided directly on the photoconductive layer without interposing the barrier layer, white spots due to electric breakdown were markedly detected while with the film of the present invention in which the barrier layer was interposed, such disadvantages were completely removed and thus clear projected images were obtained.

EXAMPLE 2 On the photoconductive layer as obtained in Example l was coated a 8.0 wt.% solution of methyl vinyl ether butyl half ester of maleic acid (GANTREZ ES- 425, supplied by GAF) and vinyl pyrrolidone vinyl acetate copolymer (7 3, supplied by GAF) in the weight ratio of 6 4 in a mixture of ethylalcohol and N,N'- dimethyl formamide (7 3) in an amount of forming a film thickness of 3 to 4p, when dried, and thus, a barrier layer was obtained. A solution comprised of chlori nated poly-N-vinyl carbazole 3g, N-vinyl carbazole 0. lg, carbon tetrabromide 0.2g. and benzene (the weight ratio of benzene to the total weight of the three compounds was 1 l) was exposed to ultraviolet irradiation and stored at a dark place and then coated on the aforementioned layer. On treating the lighttransmittable photoconductive film as in Example 1, no white spot was detected and extremely excellent lighttransmittable positive images were obtained.

EXAMPLE 3 A by weight solution of ethyl vinyl ether isopropyl half ester of maleic acid in a 7 3 ethyl alcohol methyl alcohol mixture and a 10% by weight solution of polyvinylpyrrolidone (PVP-K60, supplied by BASF) in a 7:3 ethyl alcohol N,N-dimethyl formamide mixture were mixed in the weight ratio of 4 to 6. To the resulting solution were added l/4% by weight N,N-dimethylformamide and 1/4% by weight of methyl ethyl ketone, based upon the weight of the resulting solution and further a plasticizer of 30% by weight of trichloro ethyl phosphate to prepare a 5 wt.% solution of ethyl vinyl ether isopropyl half ester of maleic acid and polyvinylpyrrolidone.

The solution so obtained was coated on a 75 1. thick polyester film including a 60% visible lighttransmittable aluminum vapor deposited layer so as to form a 4 to 5p. thick film, when dried, and thus a barrier layer was obtained. The barrier layer thus obtained, as in Example 1, was excellent in transparency, film strength, and flexibility thereof and furthermore excellent in capability to adhere to the deposited layer.

On the barrier layer was coated a photosensitive agent, which was-prepared by dissolving chlorinated poly N vinyl carbazole and Rhodamine B in a 1:1 benzene chlorobenzene mixture, in an amount of 5 to 6g/m to form a photosensitive layer.

The photosensitive film so obtained, as in Example 1, was charged and exposed to light to form microimages, which were further developed with a wet developer. As a result, positive images of high sensitivity and sharpness were obtained. On enlarging and projecting the reduced image with a projector, it was confirmed that no white spots due to electric breakdown were detected on the screen and the and a projected image of equal fidelity to the original one was obtained. Furthermore the above film has been observed to be improved greatly in respect of film strength, flexibility, and capability to adhere, which have not been observed with the conventional films.

EXAMPLE 4 A lOwt.% solution of methyl vinyl ether ethylhalf ester of maleic acid (Trade name: GANTREZ ES-225, supplied by GAF) and polyvinylpyrrolidone (Trade name: PVP K-60, supplied by GAF) in a weight ratio of 3:7 in a 7:3 ethylalcohol-formaldehyde mixture was coated on a conductively treated baryta paper to form a barrier layer of 3 to 4 ,a thickness, when dried. A photosensitive agent composed of a 1:1 benzenechlorobenzenc solution containing chlorinated poly-N- vinyl carbazole and crystal violet was coated on the above barrier layer in the amount of 4 to 6g/m The photosensitive paper so obtained was charged, exposed to light, and developed according to the known electrophotographic copying process. As a result, sharp visible images were obtained and no white spot was detected.

EXAMPLE 5 On the conductive layer as obtained in Example 1 was coated a 10 wt.% solution of methyl vinyl ether maleic anhydride copolymer and vinylpyrrolidone methacrylate copolymer (7:3) in the weight ratio of 5:5 in a 5:5 ethylalcohol-N,N-dimethyl formamide mixture to form a barrier layer of 3 to 4 ,u. thickness, when dried.

A solution comprising 3g of chlorinated poly-N-vinyl carbazole, 0.1g of N-vinyl carbazole, 0.2g of carbon tetra bromide, and benzene (the ratio of benzene to the above three components was 1 to 1) was subjected to ultraviolet irradiation, stored in a dark place, and coated on the above barrier layer.

The light-transmittable organic photoconductive film was treated in the same manner as in Example 1 and then there was obtained an extremely clear, lighttransmittable positive images which was completely free from white spots.

EXAMPLE 6 On the conductive layer as obtained in Example 1 was coated a 10 wt.% solution of methyl vinyl ether maleic anhydride copolymer and vinyl pyrrolidone acrylonitrile copolymer (7:3) in the weight ratio of 3:7 in a 5:5 ethylalcohol-N,N-dimethylformamide mixture to form a barrier layer of 3 to 4p. thickness, when dried.

A solution comprising 3g of chlorinated poly-N- vinylcarbazole, 0.1g of N-vinyl carbazole, 0.2g of carbon tetra bromide, and benzene (the ratio of the benzene to all the above three components was 1:1) was subjected to ultraviolet irradiation, stored at a dark place, and coated on the barrier layer.

The light-transmittable organic photoconductive film was treated in the same manner as in Example 1 and thus there were obtained transparent, lighttransmittable positive images which were completely free from white spots.

It can be seen from the foregoing that electric breakdown can be completely avoided by providing the barrier layer of the present invention. Furthermore sensitivity is excellent and film properties of the photosensitive layer have been markedly improved. Accordingly, light-transmittable or non light-transmittable organic electrophotographic members of great practical value can be easily produced.

EXAMPLE 7 On a 31p. thick conductive aluminum substrate was coated lOwt.% solution of methyl vinyl ether butyl ester of maleic acid (GANTREZ ES-425, supplied by GAF) and polyvinylpyrrolidone (PVP K-90, supplied by GAF) in the weight ratio of 3:7 in a 7:3 ethylalcoholformamide mixture to from a barrier layer of 2p. thickness, when dried. The barrier layer so obtained was of great transparency, strong, flexible, and the ability thereof to adhere to the aluminum substrate was excellent. Furthermore, a photosensitive agent comprising a 1:1 benzenemonochloro benzene mixture, poly N-vinyl carbazole, Rhodamine B (the molar ratio of the poly N-vinyl carbazole to Rhodamine B was 1 5X10), and a plasticizer of diphenyl chloride was coated on the barrier layer to form a 9p. thick photosensitive layer. A representative electrophotographic process comprising charging by -7.0KV corona discharge, exposing to a 500W tungusten lamp so as to obtain an exposure amount of about 40 lux. sec. and transferring the latent image onto recording paper was repeatedly applied to the photosensitive member as obtained above. The recording paper was developed with a wet developer, and it could be found that images were excellent and electric breakdown was markedly avoided as compared with the conventional master photosensitive member in which a barrier layer was not provided.

The durable repeating number was as follows:

member with no barrier layer about 100 member with a barrier layer i about 1,000

EXAMPLE 8 The photosensitive member prepared as in Example was subjected to the normal xerographic process which comprises charging by 7.0KV, exposing to light so as to obtain about 100 lux. sec. of exposure amount, developing with a wet developer, transferring to ordinary paper, and cleaning the photosensitive layer. The process was repeated and it was found that sensitivity was excellent and electric breakdown was markedly prevented by the barrier layer. The number of times that the photosensitive member was durable to repeated uses, was as follows:

photosensitive member with no barrier about 80 photosensitive member with a barrier about EXAMPLE 9 Methyl vinyl ether maleic anhyride copolymer (trade name: ANl49, supplied by GAF) and polyvinylpyrrolidone (trade name: PVP K-90, supplied by GAF) were mixed in the weight ratio of 3 to 7 and dissolved in a 3:5:2 methylalcohol-methyl ethyl ketone- N,N-dimethyl formamide mixture to prepare a wt.% solution thereof. The 10 wt.% solution was coated on a 31 ;1. thick electrically conductive aluminum substrate to provide a 1 to 2 ,u thick, when dried, barrier layer. The thus-obtained barrier layer had the same characteristics as those of the barrier layer obtained in Example 5.

On the other hand, poly N-vinyl carbazole and crystal violet in the molar ratio of 1 to 2.5 X 10' and a plasticizer Cumarone RS 1/2 (trade name, supplied by Fuji Seitetsu Co. Ltd.) were dissolved in a 1:1 benzenechlorobenzene mixture to produce a photosensitive agent. The photosensitive agent was coated on the above barrier layer to form an approximately 8 a thick photosensitive layer. With the thus-obtained photosensitive plate, the same process as in Example 5 was repeated and latent images were repeatedly transferred to a electrostatic recording paper.

The transferred electrostatic images were powderdeveloped using a magnet brush and, as a result, it was found that electric breakdown was greatly prevented. Furthermore, deterioration of the photosensitive member was extremely small and the number of times that the photosensitive members were durable to repeated uses, were as follows:

photosensitive member with no barrier layer about 90 photosensitive member with barrier layer about EXAMPLE 10 The photosensitive plate prepared in the same manner as in Example 7 was, according to a common xerographic process, charged at -7.0KV, and exposed to light so as to obtain an exposure amount of about lux.sec. on the surface thereof. Thereafter the latent images so obtained were powder-developed according to the cascade process and transferred to ordinary paper and then the photosensitive plate was cleaned. Such a process was repeated using the photosensitive plate. As a result, it was found that the photosensitive member's resistance to electric breakdown was excellent. The number of times that the photosensitive member was durable to repeated uses was as follows:

photosensitive layer having no barrier about 50 photosensitive layer having barrier about 800.

EXAMPLE 1 l Butyl vinyl ether maleic benzyl ester copolymer and polyvinylpyrralidone (PVP K-90, supplied by GAF) were mixed in the weight ratio of 4 to 6 and dissolved in a 3:3:3:l ethyl acetate methyl ethyl ketone ethyl alcohol formamide mixture to prepare a 10 wt.% solution thereof. The 10 wt% solution was coated on the same substrate as used in Example 5 to form a l to 2 p. thick dry film and thus a barrier layer was formed.

The barrier layer so obtained was of great transparency, strong, flexibile, and furthermore the ability thereof to adhere to aluminum was excellent.

On the barrier layer was coated a photosensitive material in tetrahydrofuran solution which includes 0.5 mole chlorinated poly-N-vinyl carbazole and 2,4,7- trinitro-fluorenone (the molar ratio of them is l to 1) in addition to a plasticizer of diphenyl chloride to form a thickness of about 12 ,u.. According to an electrostatic transferring process, the thus-obtained photosensitive plate was corona-discharged at 7.0KV and exposed to light so as to obtain an exposure amount of about 10 lux.sec. thereon. Thereafter the electrostatic latent image was transferred to electrostatic recording paper and developed with a wet developer. The image so formed was excellent and it was confirmed that electric breakdown was effectively prevented.

The number of times that the photosensitive layer could be used repeatedly was as follows:

photosensitive member having no barrier about photosensitive member having barrier about EXAMPLE 12 The same photosensitive plate as in Example 9 was, according to a xerographic process, charged at 7.0KV and exposed to light so as to obtain an exposure amount of about 20 lux.sec. on the surface thereof. The latent image so formed was powder-developed in accordance with the magnet brush process and transferred to ordinary paper and thereafter the photosensitive layer was cleaned. On repeating such a process it was found that the sensitivity of the photosensitive member was excellent and electric breakdown was effectively prevented. The number of times that the photosensitive plate could be used repeatedly was as follows:

photosensitive member having no barrier about photosensitive member having a barrier about EXAMPLE 13 As the conductive substrate there was used a 100 p. thick sand scratched aluminum plate, on which a barrier layer was provided in the same manner as in Example 9.

A photosensitive solution composed of benzene and chlorobenzene l:l which included 0.5 mole chlorinated poly-N-vinylcarbazole and Rhodamine B (the molar ratio of them was 1 X and further included a plasticizer, 0.5g of diphenyl chloride was coated on the barrier layer to form a dry film of 4 p. thickness. The thus-obtained photosensitive plate was, according to an electrostatic transferring process, charged at -7.0KV and exposed to light at about 40 lux.sec. and the resulting image was transferred to electrostatic recording paper. Such a process was repeated. The electrostatic recording paper was developed by a wet developer and, as a result, it was found that electric breakdown was greatly prevented. The durable repeating number was as follows:

photosensitive member having no barrier layer about 100 photosensitive member having a barrier about EXAMPLE l4 l-lexyl vinyl ether maleic benzyl ester and polyvinylpyrrolidone (PVP K-90, supplied by GAF) were mixed in the weight ratio of 5:5 and dissolved in a 4:4:2 methyl ethyl ketone/ N,N'-dimethyl formamide methyl alcohol mixture to prepare a 10 wt.% solution thereof. The resulting solution was coated on conductively treated baryta paper to form a dry film of 3 to 4 ,u. thickness and thus there was formed a barrier layer.

The barrier layer had the same film properties as that of Example 5. A photosensitive agent solution of tetrahydrofuran which included 0.5 mole chlorinated poly N-vinylcarbazole and 2,4,7-trinitrofluorenone (1:1 molar ratio) and further included 0,5g of diphenyl chloride as a plasticizer was coated on the barrier layer to provide an approximately 12 ,u. thick layer.

The thus-obtained photosensitive plate was, according to an electrostatic transferring process charged at 7.0KV and exposed to light at about 5 lux.sec. and the resulting image was transferred to electrostatic recording paper. Such a process was repeated. The electrostatic recording paper was developed with magnet brush process and thus there was obtained an excellent image and it was also confirmed that resistance to electric breakdown was improved. The durable repeating number was as follows:

photosensitive member having no barrier about 400 photosensitive member having a barrier about EXAMPLE On a 100 ,1. thick polyester film having a 70% light transmittable aluminum vacuum evaporated layer was coated on 8 wt.% solution of methyl vinyl ether maleic anhydride (trade name: AN-l69, supplied by GAF) and vinyl pyrrolidone vinyl ether copolymer, which was prepared by dissolving methyl vinyl ether maleic anhydride and vinylpyrrolidone vinyl ether copolymer of the weight ratio of 4 to 6 in an ethyl acetate 4 methyl ethyl ketone 3 formamide 3 mixture, to form a l to 2 [.L thick dry film and thus there was obtained a barrier layer.

The thus-obtained barrier layer had the same film properties as those of the barrier layer obtained in Example 5.

A photosensitive agent, which was prepared by dissolving poly-N-vinyl carbazole and Crystal Violet (in the molar ratio of l to 2.5 X 10*) together with a plasticizer of 0.5g of diphenyl chloride in a benzene chlorobenzene (1:1) mixture, was coated on the above barrier layer to form a dry film of about 4n thickness.

The photosensitive plate so obtained was charged at 7.0KV and exposed to light at about 100 lux.sec. according to the electrostatic transferring method, and the images formed were transferred to electrostatic recording paper repeatedly. The transferred image was developed with a liquid developer and, as a result, it was observed that the effect of preventing electric breakdown of the barrier was considerably excellent.

The number of times that the photosensitive member could be used repeatedly was as follows:

photosensitive member with no barrier layer about 300 photosensitive member with a barrier layer about EXAMPLE 16 On an electrically conductive substrate composed of an aluminum plate (thickness of 31p.) was coated a 15wt.% solution of methyl vinyl ether maleic benzyl ester and vinylpyrrolidone vinyl acetate copolymer (the weight ratio of 6:4) in a acetic acid ethyl alcohol N,N-dimethyl formamide (325:5) mixture to prepare a dry film of 3 to 4p. thickness, and thus a barrier layer was formed.

On the thus-formed barrier layer was coated the same photosensitive compound as in Example 9 to form a about 10p. thick photosensitive layer.

The formed photosensitive plate was repeatedly used in the electrostatic transferring process comprising charging at 7.0KV, exposing to light so as to obtain about 10 lux. sec. of exposure amount, and thereafter transferring electrostatic images to electrostatic recording paper.

On developing the images, excellent printed images were obtained and the effect of preventing electric breakdown of the barrier layer was observed. The number of times that the photosensitive plate could be used repeatedly was as follows:

photosensitive member with no barrer layer about photosensitive member with barrier layer about EXAMPLE 17 The following photosensitive layer was used in the foregoing Examples.

3g of poly-9-vinyl carbazole (Lunican M-l) was dissolved in 45ml of mono chloro benzene, to which vinylidene chloride-methyl methacrylate copolymer and 0.0l5g of 3,3'-di-n-octhyl-6,6'-dinitro-2,2'- thiacarbocyanine tosylate were added to prepare a photosensitive liquid.

The barrier layers usedin the foregoing Examples were used.

The photosensitive liquid was coated on the barrier layer so as to form a Su thick dry film.

13 The ratio of vinylidene chloride to methylacrylate in the copolymer thereof and the addition amount of the copolymer were shown below.

Run No. Added Transamount parency Flexibility Ratio of comonomers (mol :mol)

Specific Sensitivity EXAMPLE 18 Into 40ml of monochlorobenzene was dissolved 3g of chlorinated poly-9-vinylcarbazole (chlorine content: 7.5%) and 0.015g of 1,1 -n-octyl-3,3,3',3-tetramethyl- 5,5-dinitro-2,2'-pentamethine tosylate to prepare a homogeneous solution. To the homogeneous solution was added 0.6g of Cumaron LCR (cumarone resin produced by Shin Nippon Seitetsu), 0.75g Enpara 4O (chlorinated parrafin produced by Azinomoto) and a vinylidene chloride-methyl acrylate copolymer (the ratio of vinylidene chloride to methyl acrylate; 1 mol 3 mol, molecular weight; 400,000) to prepare a photosensitive liquid.

The same barrier layers as in the foregoing Examples were used.

The photosensitive liquid was coated on the barrier layer to form a 5p. thick layer and thus a photosensitive plate was prepared.

The addition amount of vinylidene chloride-methyl acrylate copolymer and the properties of the photosensitive plate are shown below.

Run No. Amount of E 1/10 Capability Flexibility copolymer Specific to adhere (g) sensitivity 1 100 X X 2 0.03 100 A-O O 3 0.06 95 O O 4 0.1 92 (D (9 5 0.2 80 (9 6 0.5 77

10 microns for preventing electric deterioration and fatigue due to repeated use, said intermediate barrier layer consisting essentially of (1) a copolymer of maleic anhydride and an alkyl vinyl ether wherein the alkyl moiety thereof has from 1 to 12 carbon atoms or (2) mixtures of (a) copolymers of alkyl vinyl ethers wherein the alkyl moiety thereof has from 1 to 12 carbon atoms and alkyl half esters of maleic acid and (b) homopolymers of vinyl pyrrolidone having an average molecular weight of from 4,000 to 360,000 or copolymers of vinyl pyrrolidone with vinyl monomers copolymerizable therewith having an average molecular weight of from 4,000 to 360,000; and overlying said intermediate barrier layer a photoconductive layer consisting essentially of an organic photoconductor and from 1 to 10% by weight, based on the weight of the organic photoconductor, of a copolymer of vinylidene chloride and an acrylic acid alkyl ester.

2. The electrophotographic photosensitive member of claim 1, wherein the alkyl moiety of said alkyl vinyl ether has from 1 to 6 carbon atoms.

3. The electrophotographic photosensitive member of claim 1, wherein the alkyl moiety of said alkyl half esters of maleic acid has from 1 to 8 carbon atoms.

4. The electrophotographic photosensitive member of claim 3, wherein said alkyl moiety includes arylsubstitue alkyl groups.

5. The electrophotographic photosensitive member of claim 4, wherein said aryl-substituted alkyl group is benzyl.

6. The electrophotographic photosensitive member of claim 1, wherein the average molecular weight of said vinyl pyrrolidone homopolymer or copolymer is from 40,000 to 360,000.

7. The electrophotographic photosensitive member of claim 1, wherein said vinyl monomers are selected from the group consisting of styrene, vinyl chloride, vinyl acetate, methacrylate, acrylate, acrylamide, acrylonitrile, vinyl ethers, vinyl imidazole and ethylene.

8. The electrophotographic photosensitive member of claim 7, wherein the molar ratio of vinyl monomer to vinyl pyrrolidone is from seven-thirds to threesevenths.

9. The electrophotographic photosensitive member of claim 1, wherein said substrate is composed of a material having a volume resistivity of below 10 ohm/cm.

10.. The electrophotographic photosensitive member of claim 1, wherein the thickness of said barrier layer is from 2 to 7 microns.

11. The electrophotographic photosensitive member of claim 1, wherein the volume resistivity of the barrier layer is from 10 to 10 ohm/cm.

12. The electrophotographic photosensitive member of claim 1, wherein said organic photoconductor is composed of 9-vinyl carbazole, derivatives thereof or a polymer thereof.

13. The electrophotographic photosensitive member of claim 1, wherein said photoconductive layer further includes a sensitizator for said organic photoconductor.

14. The electrophotographic photosensitive member of claim 1,. wherein said barrier layer consists essentially of an unsaponified copolymer of maleic anhydride and an alkyl vinyl ether wherein the alkyl moiety thereof has from 1 to 12 carbon atoms.

15. The electrophotographic photosensitive member of claim 1, wherein said intermediate barrier layer consists essentially of a mixture of said copolymer of maleic anhydride and an alkyl vinyl ether with said homopolymers or copolymers of vinyl pyrrolidone. 

1. AN ELECTROPHOTOGRAPHIC PHOTOSENSITIVE MEMBER COMPRISING A SUPPORT; AND OVERLYING SAID SUPPORT AN INTERMEDIATE BARRIER LAYER HAVING A THICKNESS OF LESS THAN 10 MICRONS FOR PREVENTING ELECTRIC DETERIORATION AND FATIGUE DUE TO REPEATED USE, SAID INTERMEDIATE BARRIER LAYER CONSISTING ESSENTIALLY OF (1) A COPOLYMER OF MALEIC ANHYDRIDE AND AN ALKYL VINYL ETHER WHEREIN THE ALKYL MOIETY THEREOF HAS FROM 1 TO 12 CARBON ATOMS OR (2) MIXTURES OF (A) COPOLYMERS OF ALKYL VINYL ETHERS WHEREIN THE ALKYL MOIETY THEREOF HAS FROM 1 TO 12 CARBON ATOMS AND ALKYL HALF ESTERS OF MALEIC ACID AND (B) HOMOPOLYMERS OF VINYL PYRROLIDONE HAVING AN AVERAGE MOLECULAR WEIGHT OF FROM 4,000 TO 360,000 OR COPOLYMERS OF VINYL PYRROLIDONE WITH VINYL MONOMERS COPOLYMERIZABLE THEREWITH HAVING AN AVERAGE MOLECULAR WEIGHT OF FROM 4,000 TO 360,000; AND OVERLYING SAID INTERMEDIATE BARRIER LAYER A PHOTOCONDUCTIVE LAYER CONSISTING ESSENTIALLY OF AN ORGANIC PHOTOCONDUCTOR AND FROM 1 TO 10% BY WEIGHT, BASED ON THE WEIGHT OF THE ORGANIC PHOTOCONDUCTOR, OF A COPOLYMER OF VINYLIDENE CHLORIDE AND AN ACRYLIC ACID ALKYL ESTER.
 1. An electrophotographic photosensitive member comprising a support; and overlying said support an intermediate barrier layer having a thickness of less than 10 microns for preventing electric deterioration and fatigue due to repeated use, said intermediate barrier layer consisting essentially of (1) a copolymer of maleic anhydride and an alkyl vinyl ether wherein the alkyl moiety thereof has from 1 to 12 carbon atoms or (2) mixtures of (a) copolymers of alkyl vinyl ethers wherein the alkyl moiety thereof has from 1 to 12 carbon atoms and alkyl half esters of maleic acid and (b) homopolymers of vinyl pyrrolidone having an average molecular weight of from 4,000 to 360,000 or copolymers of vinyl pyrrolidone with vinyl monoMers copolymerizable therewith having an average molecular weight of from 4,000 to 360,000; and overlying said intermediate barrier layer a photoconductive layer consisting essentially of an organic photoconductor and from 1 to 10% by weight, based on the weight of the organic photoconductor, of a copolymer of vinylidene chloride and an acrylic acid alkyl ester.
 2. The electrophotographic photosensitive member of claim 1, wherein the alkyl moiety of said alkyl vinyl ether has from 1 to 6 carbon atoms.
 3. The electrophotographic photosensitive member of claim 1, wherein the alkyl moiety of said alkyl half esters of maleic acid has from 1 to 8 carbon atoms.
 4. The electrophotographic photosensitive member of claim 3, wherein said alkyl moiety includes aryl-substitue alkyl groups.
 5. The electrophotographic photosensitive member of claim 4, wherein said aryl-substituted alkyl group is benzyl.
 6. The electrophotographic photosensitive member of claim 1, wherein the average molecular weight of said vinyl pyrrolidone homopolymer or copolymer is from 40,000 to 360,000.
 7. The electrophotographic photosensitive member of claim 1, wherein said vinyl monomers are selected from the group consisting of styrene, vinyl chloride, vinyl acetate, methacrylate, acrylate, acrylamide, acrylonitrile, vinyl ethers, vinyl imidazole and ethylene.
 8. The electrophotographic photosensitive member of claim 7, wherein the molar ratio of vinyl monomer to vinyl pyrrolidone is from seven-thirds to three-sevenths.
 9. The electrophotographic photosensitive member of claim 1, wherein said substrate is composed of a material having a volume resistivity of below 109ohm/cm.
 10. The electrophotographic photosensitive member of claim 1, wherein the thickness of said barrier layer is from 2 to 7 microns.
 11. The electrophotographic photosensitive member of claim 1, wherein the volume resistivity of the barrier layer is from 1010 to 1011 ohm/cm.
 12. The electrophotographic photosensitive member of claim 1, wherein said organic photoconductor is composed of 9-vinyl carbazole, derivatives thereof or a polymer thereof.
 13. The electrophotographic photosensitive member of claim 1, wherein said photoconductive layer further includes a sensitizator for said organic photoconductor.
 14. The electrophotographic photosensitive member of claim 1, wherein said barrier layer consists essentially of an unsaponified copolymer of maleic anhydride and an alkyl vinyl ether wherein the alkyl moiety thereof has from 1 to 12 carbon atoms. 